The long term goal of this research is to define the mechanisms bywhich photoperiod, hormones of the hypothalamus, pituitary andovary interact in controlling cessation and reinitiation ofembryonic development and implantation in a species exhibitingobligate delay of implantation. This proposal specifically seeksto Provide additional evidence to support the theory that corporalutea of mustelid carnivores such as the domesticated ferret andspotted skunk secrete a proteinacious compound that is essentialfor induction of blastocyst implantation. I propose to furtherpurify and chemically characterize the ferret luteal implantationfactor (LIF) and to determine which trophic factor(s) stimulate itssynthesis and secretion in vitro. I then propose to demonstrateby passive immunization of ferrets and spotted skunks, thatantibodies to LIF will inhibit implantation. Another experimentis designed to determine on which days of pregnancy orpseudopregnancy LIF is secreted in ferrets. I also propose tofurther verify that LIF is only produced by CL of ferrets and toexplore its subcellular distribution and mode of secretion usingimmunocytochemistry. Another series of experiments is designed todetermine whether LIF acts on the uterus and or blastocysts and toprovide evidence for the presence of receptor sites to thiscompound. This will be accomplished by studying specific bindingof (125I)-LIF to uterine and blastocyst plasma membranes. Furtherdemonstration of specific receptor sites will be accomplished byextraction of cross-linked (125I)-LIF-receptor complexes, followedby electrophoresis and autoradiography. The last set ofexperiments is designed to determine the specific effects of LIFon its target organs by measuring such things as changes in cAMP,protein, RNA and DNA synthesis in the uterus and or blastocysts.